The research program will study the biology of neurotransmitter systems in brain, among which are dopamine, serotonin an the opioid and opioid related systems, that may play a role in drug reward. Using the genes encoding the human receptors for these and related transmitters we aim to elucidate aspects of receptor function. Since recent work from this laboratory has provided evidence for receptor dimerization a priority is placed on the elucidation of the role of the homodimers in receptor function, the structural determinants of receptor dimer formation, and to screen for dimer monomer selective drugs. Cotransfection of closely related receptors in cell lines will determine whether heterodimers can also form. The research proposal will also focus on receptor G-protein interactions, second messenger activation, the receptor posttranslational modifications of palmitoylation and phosphorylation, the mechanism of receptor desensitization, visualization of cell surface receptor trafficking using confocal microscopy, and characterization of several newly discovered receptor genes. A method for purification of the dopamine and opioid receptors has been established, using affinity resins, and it is now possible to visualize these receptors. A colony of healthy D1 receptor knockout mice has demonstrated a marked reduction of responding for substances of abuse demonstrating that this single gene disruption can attenuate drug seeking behaviors. The experimental approach will integrate behavioural and genetic studies with the molecular and biochemical approaches, and will study alterations in the behaviour resulting from manipulation or deletion of specific receptor genes and the functional consequences in animal models. Candidate receptor and transporter genes, in the dopamine and serotonin families, have been selected and will be screened using single stranded conformational polymorphism analysis for changes in structure in drug abuse patient populations.